This thread is quite old and I'm sure the original poster has already made their decision on a replacement for their GH2. However, today an obvious upgrade would be the G7. The G7 is inexpensive and provides nearly everything a GH2 user would want in an upgrade - the key missing items being in body image stabilization and true multi-format framing. Otherwise, the G7 is essentially the GH2 all over again but with everything improved and enhanced. Everything about the G7 feels completely normal to a GH2 user so there is a short learning curve that only applies to the new features. Those new features include focus peaking, 4K video, post focus and wireless operation to name the key ones.
Perhaps the nicest improvement in the G7 is the physical ergonomics. The GH2 hand-fit was not ideal and frequent bumping of the ISO and white balance buttons were common complaints. The G7, while being nearly exactly the same size as the GH2, somehow makes the hand fit just about perfect. Panasonic relocated the buttons slightly and added more thumb room. They also changed the actual switches making them less prone to accidental bumping and then added an optional lock out for the main controller button panel. The G7 is more comfortable to hold and accidental setting changes are rare. Throw in the enhanced view finder, the dual control wheels and all the other goodies and it's a no-brainer upgrade.